In semiconductor production, chemical industries, or the like, a bellows pump may be used as a pump for feeding a fluid such as a chemical solution, a solvent, or the like.
For example, as disclosed in PATENT LITERATURE 1, in the bellows pump, pump cases are connected to both sides of a pump head in a right-left direction (horizontal direction) to form two air chambers, and a pair of bellows that are expandable/contractible in the right-left direction are provided within the respective air chambers, and the bellows pump is configured such that each bellows is contracted or expanded by alternately supplying pressurized air to the respective air chambers.
In the pump head, a suction passage and a discharge passage for the fluid are formed so as to communicate with the interior of each bellows, and further check valves are provided which permit flow of the fluid in one direction in the suction passage and the discharge passage and blocks flow of the fluid in another direction in the suction passage and the discharge passage. The check valve for the suction passage is configured: to be opened by expansion of the bellows, to permit flow of the fluid from the suction passage into the bellows; and to be closed by contraction of the bellows, to block flow of the fluid from the interior of the bellows to the suction passage. In addition, the check valve for the discharge passage is configured: to be closed by expansion of the bellows, to block flow of the fluid from the discharge passage into the bellows; and to be opened by contraction of the bellows, to permit flow of the fluid from the interior of the bellows to the discharge passage.
The pair of bellows are integrally connected to each other by a tie rod. When one of the bellows contracts to discharge the fluid to the discharge passage, the other bellows forcedly expands at the same time, so that the fluid is sucked from the suction passage. In addition, when the other bellows contracts to discharge the fluid to the discharge passage, the one bellows forcedly expands at the same time, so that the fluid is sucked from the suction passage.
In the bellows pump having the above configuration, a phenomenon (pulsation) that a discharge pressure instantly falls to approximately zero at time of switching between discharge and suction of the fluid, is a problem. In the conventional art, in order to suppress this pulsation, an accumulator (pressure accumulator) is mounted at the discharge side of the bellows pump (see, e.g., PATENT LITERATURE 2), or a bellows pump in which an accumulator is incorporated in place of one of a pair of bellows (see, e.g., PATENT LITERATURE 3) is used.